1. Field of the Invention
The present invention relates to an in-wheel motor system for use in a vehicle having direct drive wheels as drive wheels and, particularly, to a structure for mounting a member for interconnecting the rotor side of a motor and a wheel to the wheel and a method of installing the same.
2. Description of the Prior Art
It is generally known that, in a vehicle having a suspension mechanism such as a spring around a wheel, as the mass of parts under the spring such as a wheel, knuckle and suspension arm, so-called “unsprung mass” increases, changes in the ground load of a tire when running on an uneven road become larger, thereby deteriorating road holding properties.
In a vehicle driven by a motor such as an electric car, an in-wheel motor system incorporating a motor in a wheel is being employed. However, in a conventional in-wheel motor which is fixed to a spindle shaft connected to a part such as an upright or knuckle which is one of parts around a wheel of the vehicle so that a motor rotor and a wheel can turn, the above unsprung mass increases by the weight of the in-wheel motor, whereby changes in the ground load of the tire become large, thereby deteriorating road holding properties (refer to patent documents 1 to 3, for example).
To solve the above problem, the present applicant proposes an in-wheel motor system in which an in-wheel motor is installed below the spring of a vehicle by a buffer member or buffer system to be float mounted below the spring of the vehicle in order to greatly reduce changes in the ground load of a tire, thereby making it possible to improve the road holding properties of the vehicle (refer to patent document 4, for example).
FIG. 6 shows an improved version of the above in-wheel motor system. In this in-wheel motor system, a non-rotating side case 3a supporting the stator 3S of a hollow in-wheel motor 3 and a knuckle 5 are interconnected by a buffer mechanism 10 a shock absorber 12 composed of comprising a direct-acting guide member 11 for guiding in the vertical direction of the vehicle, a spring member expanding and contracting in the moving direction of this direct-acting guide member 11 and a damper to float mount the above motor 3 below the spring, and a rotating side case 3b supporting the rotor 3R of the above motor 3 and a wheel 2 are interconnected by a flexible coupling 20 comprising a hollow disk-like motor side plate 21 mounted to the rotating side case 3b of the motor, a hollow disk-like wheel side plate 22 mounted to the wheel 2, and a plurality of cross guides 23 for interconnecting the above plates 21 and 22, whose moving directions on the front and rear sides cross each other, so as to transmit the torque of the above motor 3 to the above wheel 2.
As shown in FIG. 7, each of the above cross guides 23 consists of a motor side guide rail 23A mounted to the motor side plate 21, a wheel side guide rail 23B mounted to the wheel side plate 22, and a cross guide body 23C having guide grooves 23a and 23b on the top surface and the under surface. The motor side guide rail 23A and the wheel side guide rail 23B can move along the guide grooves 23a and 23b of the cross guide body 23C in crossing directions. The above cross guide 23 is installed such that the moving direction of the above guide rail 23A becomes 45° from the radial direction of the above plate 21, whereby the above plates 21 and 22 can move in the vertical direction of the vehicle.
Thereby, the above motor 3 is elastically supported to the knuckle 5 which is a part around the wheel of the vehicle, torque is transmitted to the wheel 2 efficiently, and the motor 3 can move only in the vertical direction. Therefore, the road holding properties of the vehicle can be improved by reducing changes in the ground load of the tire. Even when the motor shaft becomes eccentric to the wheel shaft, as the flexible coupling 20 comprises the above cross guides 23, the guide rails 23A and 23B of the above cross guides 23 slide to absorb the above eccentricity.
Patent document 1: Japanese Patent No. 2676025
Patent document 2: Japanese Examined Patent Publication No. 9-506236
Patent document 3: Japanese Unexamined Patent Application No. 10-305735
Patent document 4: WO 02/083446 A1